A typical internal combustion engine may include an air intake manifold including dual flow paths between a throttle valve and engine combustion chambers. The dual flow paths typically include a long runner plenum and long runner passages, and a short runner plenum and short runner passages. A short runner valve closes to block the short runner passages and thereby force airflow through the long runner plenum and long runner passages. Conversely, the short runner valve opens to unblock the short runner passages and thereby permit airflow through both of the dual flow paths. Thus, the short runner valve controls airflow through the long and short runners, to optimize volumetric efficiency of the engine at both high and low engine speed ranges.
It is desirable to verify that the short runner valve is operating properly in order to ensure desired engine emissions performance. The short runner valve operation may be diagnosed using a valve position sensor, but that approach requires additional hardware and software and, thus, increases the cost of the engine.